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117-685: The Arve Valley consists of the upper reaches of the river Arve, whose source is in the Mont Blanc massif , on the Savoyard Col-du-Balme side. Down stream, the river passes through the plain of Annemassy, before emptying into the Rhône in the Swiss canton of Geneva. The Valley came into being during the last ice age when the Alpine glaciers extended beyond Geneva. There is controversy over

234-400: A beta decay reaction may interact in a distant detector as a muon or tau neutrino, as defined by the flavor of the charged lepton produced in the detector. This oscillation occurs because the three mass state components of the produced flavor travel at slightly different speeds, so that their quantum mechanical wave packets develop relative phase shifts that change how they combine to produce

351-749: A body on the Glacier du Talèfre, close to the Couvercle Hut. It was identified as that of a young Chamonix guide who had been caught in a winter storm during a solo ascent of the Nant Blanc face of the Aiguille Verte in 1982 and was assumed to have fallen into a crevasse. In 2013, a box of valuable gemstones was found by a climber on the Bossons Glacier. It had re-emerged, having been carried 3,048 metres (10,000 ft) downhill from

468-483: A code of practice put in place which requires an annual declaration of all finds to be made. It also gives a right for the Chamonix crystal museum (Musée des Cristaux) to have first option to acquire specimens of significance for its collections. To further protect the scientific value of material collected, all specimens offered for sale must be labelled with details of where they were found. The crystal museum opened to

585-408: A consequence. For example, an electron neutrino produced in a beta decay reaction may interact in a distant detector as a muon or tau neutrino. The three mass values are not yet known as of 2024, but laboratory experiments and cosmological observations have determined the differences of their squares, an upper limit on their sum (<  2.14 × 10  kg ), and an upper limit on the mass of

702-628: A difference between the neutrino and antineutrino could simply be due to one particle with two possible chiralities. As of 2019 , it is not known whether neutrinos are Majorana or Dirac particles. It is possible to test this property experimentally. For example, if neutrinos are indeed Majorana particles, then lepton-number violating processes such as neutrinoless double-beta decay would be allowed, while they would not if neutrinos are Dirac particles. Several experiments have been and are being conducted to search for this process, e.g. GERDA , EXO , SNO+ , and CUORE . The cosmic neutrino background

819-576: A distance of just 8 kilometres (5.0 mi). Because of its great elevation, much of the massif is snow- and ice-covered, and has been deeply dissected by glaciers. The Mer de Glace is the longest glacier in the range as well as the longest in France and the second longest in the Alps. The debris-covered Miage Glacier on the southern side of the massif is the longest in Italy. The summit of Mont Blanc

936-504: A gamma ray. The coincidence of both events—positron annihilation and neutron capture—gives a unique signature of an antineutrino interaction. In February 1965, the first neutrino found in nature was identified by a group including Frederick Reines and Friedel Sellschop . The experiment was performed in a specially prepared chamber at a depth of 3 km in the East Rand ("ERPM") gold mine near Boksburg , South Africa. A plaque in

1053-605: A laboratory, but is predicted to happen within stars and supernovae. The process affects the abundance of isotopes seen in the universe . Neutrino-induced disintegration of deuterium nuclei has been observed in the Sudbury Neutrino Observatory, which uses a heavy water detector. There are three known types ( flavors ) of neutrinos: electron neutrino ν e , muon neutrino ν μ , and tau neutrino ν τ , named after their partner leptons in

1170-658: A meagre harvest of rye and oats . Some farmers in the valley of Chamonix joined their counterparts from the neighbouring valleys of Maurienne , Beaufortain and Tarentaise and crossed the Alps into southern Germany, Austria and northern Italy to sell their products and bring back goods for sale in local markets. In 1741, the Chamouny valley and its glaciers on the north side of the massif were discovered and written about by two aristocratic travelling Englishmen, named William Windham and Richard Pococke . The descriptions of their exploits were published across Europe, bringing

1287-473: A new major field of research that still continues. Eventual confirmation of the phenomenon of neutrino oscillation led to two Nobel prizes, one to R. Davis , who conceived and led the Homestake experiment and Masatoshi Koshiba of Kamiokande, whose work confirmed it, and one to Takaaki Kajita of Super-Kamiokande and A.B. McDonald of Sudbury Neutrino Observatory for their joint experiment, which confirmed

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1404-579: A number of articles on the flora around the Mont Blanc area, including a list of the flowering plants, ferns mosses and lichens found at les Grands Mulets and elsewhere in the massif around Chamonix and the Aosta Valley. High up in the middle of the Glacier de Talèfre, completely surrounded by ice, and due south of Les Droites, lies a large triangular region of steep mountainside containing an unusual mixture of high-alpine vegetation. Known as

1521-566: A process analogous to light traveling through a transparent material . This process is not directly observable because it does not produce ionizing radiation , but gives rise to the Mikheyev–Smirnov–Wolfenstein effect . Only a small fraction of the neutrino's energy is transferred to the material. Onia For each neutrino, there also exists a corresponding antiparticle , called an antineutrino , which also has no electric charge and half-integer spin. They are distinguished from

1638-418: A proton, electron, and the smaller neutral particle (now called an electron antineutrino ): Fermi's paper, written in 1934, unified Pauli's neutrino with Paul Dirac 's positron and Werner Heisenberg 's neutron–proton model and gave a solid theoretical basis for future experimental work. By 1934, there was experimental evidence against Bohr's idea that energy conservation is invalid for beta decay: At

1755-553: A significant impact on the environment and on human activity. In 1892, a large body of water which had accumulated under the surface of the Tête Rousse Glacier , burst suddenly on the night of 11 July. It released 200,000 cubic metres (7,100,000 cu ft) of water and ice which flowed down the mountainside, killing 175 people in Saint-Gervais. The recent rediscovery of a further build-up of water deep within

1872-700: A small population of albino marmots within Val Ferret). Eurasian lynx have been reintroduced into the French Alps and, although present around the Mont Blanc massif, are extremely unlikely to be encountered. Over 80 different bird species have been recorded on the Italian side of the massif from within Val Ferret, including 63 nesting species and nine regional or national rarities. The following birds have been recorded in different habitats right across

1989-605: A varying superposition of three flavors. Each flavor component thereby oscillates as the neutrino travels, with the flavors varying in relative strengths. The relative flavor proportions when the neutrino interacts represent the relative probabilities for that flavor of interaction to produce the corresponding flavor of charged lepton. There are other possibilities in which neutrinos could oscillate even if they were massless: If Lorentz symmetry were not an exact symmetry, neutrinos could experience Lorentz-violating oscillations . Neutrinos traveling through matter, in general, undergo

2106-499: Is 46 kilometres (29 mi) long and lies in a southwest to northeasterly direction across the borders of France ( Haute-Savoie and Savoie ), Italy ( Aosta Valley ) and Switzerland (western Valais ). At its widest point the massif is 20 km (12 mi) across. The northwestern side of the massif lies mostly within France, and is bounded by the valley of the Arve , containing the towns of Argentière , Chamonix and Les Houches . To

2223-472: Is also a probe of whether neutrinos are Majorana particles , since there should be a different number of cosmic neutrinos detected in either the Dirac or Majorana case. Neutrinos can interact with a nucleus, changing it to another nucleus. This process is used in radiochemical neutrino detectors . In this case, the energy levels and spin states within the target nucleus have to be taken into account to estimate

2340-516: Is an ice cap whose thickness varies from year to year. The entire massif can be circumnavigated by the Tour du Mont Blanc , a walking route of approximately 170 kilometres (110 mi). It usually takes around 11 days to complete, but is also used for an annual mountain ultramarathon , with top competitors expected to complete the whole route in less than 21 hours. The main mountain passes, or cols , that connect different valleys and towns around

2457-545: Is associated with the correspondingly named charged lepton . Although neutrinos were long believed to be massless, it is now known that there are three discrete neutrino masses with different tiny values (the smallest of which could even be zero ), but the three masses do not uniquely correspond to the three flavors: A neutrino created with a specific flavor is a specific mixture of all three mass states (a quantum superposition ). Similar to some other neutral particles , neutrinos oscillate between different flavors in flight as

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2574-517: Is bounded to the east by a separate valley, confusingly also called Val Ferret , and which separates it from the Pennine Alps . Its watercourse, la Dranse de Ferret , flows northwards to join the Rhône at Martigny . The west side of the northern end of the massif is drained by the Trient , also joining the Rhône near Martigny. The borders of all three countries converge at a tripoint near

2691-493: Is conventionally called the "normal hierarchy", while in the "inverted hierarchy", the opposite would hold. Several major experimental efforts are underway to help establish which is correct. A neutrino created in a specific flavor eigenstate is in an associated specific quantum superposition of all three mass eigenstates. The three masses differ so little that they cannot possibly be distinguished experimentally within any practical flight path. The proportion of each mass state in

2808-581: Is distributed fairly evenly over all months of the year, and mostly originates from a westerly airflow. There is, however, significant variation in precipitation with altitude. For example, Chamonix has an elevation of approximately 1,030 metres (3,380 ft) and receives around 1,020 mm (40 in) of annual precipitation, whilst the Col du Midi, which is at 3,500 metres (11,500 ft) above sea level, receives significantly more, totalling 3,100 mm (122 in). However, at an even higher altitude (near to

2925-404: Is further influenced by the different aspects of the faces, by the geology, and by the influence of man on the lower and middle slopes where forest clearance has created open grassland . The native forest habitats are essential for the survival of many species, with the key conifer species including larch, pine, stone pine and red pine. Over a thousand plant species have been recorded across

3042-463: Is important to understand because many neutrinos emitted by fusion in the Sun pass through the dense matter in the solar core (where essentially all solar fusion takes place) on their way to detectors on Earth. Starting in 1998, experiments began to show that solar and atmospheric neutrinos change flavors (see Super-Kamiokande and Sudbury Neutrino Observatory ). This resolved the solar neutrino problem:

3159-439: Is known today that at least 68 separate mineral species occur across the whole range of the Mont Blanc massif. In order to preserve the mineralogical heritage of Mont Blanc, in 2008 the commune of Chamonix banned all mineral-hunting activities and collection of specimens without a prior permit being issued by the mayor 's office. Use of explosives , heavy machinery or helicopters for removing material were also banned, and

3276-505: Is located at 2,173 m (7,129 ft) above sea level, and is the highest botanical garden in Europe. It contains around 800 plant species and covers an area of 7,000 square metres (75,000 sq ft). It was originally created in 1987 just as a tourist attraction but, with the subsequent designation of the adjacent Pavillon du Mont Frety as a protected area, it has since increased in scientific importance. It can be reached either from

3393-401: Is located has been occupied by humans for at least 70,000 years, although, as now—and because of the great height and glaciated nature of the mountains—only the lower parts of the valleys around its perimeter would have been inhabited or used as routes of communication. The Romans, who occupied the region 2,000 years ago, used the main valleys around the massif for military purposes. They gave

3510-575: Is named after Mont Blanc (4,808 metres (15,774 ft)), the highest point in western Europe and the European Union . Because of its considerable overall altitude, a large proportion of the massif is covered by glaciers , which include the Mer de Glace and the Miage Glacier  – the longest glaciers in France and Italy, respectively. The massif forms a watershed between

3627-533: Is no experimental evidence for a non-zero magnetic moment in neutrinos. Weak interactions create neutrinos in one of three leptonic flavors : electron neutrinos ( ν e ), muon neutrinos ( ν μ ), or tau neutrinos ( ν τ ), associated with the corresponding charged leptons, the electron ( e ), muon ( μ ), and tau ( τ ), respectively. Although neutrinos were long believed to be massless, it

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3744-456: Is now known that there are three discrete neutrino masses; each neutrino flavor state is a linear combination of the three discrete mass eigenstates. Although only differences of squares of the three mass values are known as of 2016, experiments have shown that these masses are tiny compared to any other particle. From cosmological measurements, it has been calculated that the sum of the three neutrino masses must be less than one-millionth that of

3861-401: Is significantly less than that in either Courmayeur or Chamonix. The massif contains a very rich variety of biodiversity as a result of the huge height range and different habitats found between the valleys and the highest summits. Mild temperatures occur at altitudes between 600 and 1,000 metres (2,000 and 3,300 ft), whereas arctic conditions occur from 2,500 metres (8,200 ft) up to

3978-595: Is so small ( -ino ) that it was long thought to be zero . The rest mass of the neutrino is much smaller than that of the other known elementary particles (excluding massless particles ). The weak force has a very short range, the gravitational interaction is extremely weak due to the very small mass of the neutrino, and neutrinos do not participate in the electromagnetic interaction or the strong interaction . Thus, neutrinos typically pass through normal matter unimpeded and undetected. Weak interactions create neutrinos in one of three leptonic flavors : Each flavor

4095-475: The 1995 Nobel Prize . In this experiment, now known as the Cowan–Reines neutrino experiment , antineutrinos created in a nuclear reactor by beta decay reacted with protons to produce neutrons and positrons: The positron quickly finds an electron, and they annihilate each other. The two resulting gamma rays (γ) are detectable. The neutron can be detected by its capture on an appropriate nucleus, releasing

4212-746: The Dora Baltea towards Aosta , eventually joining the Po. However, the extreme western end of the southern side of the massif does lie within France and is bounded by the Vallée des Glaciers (which connects to the Val Veny over the watershed of the col de la Seigne), and its waters flow southwards towards the Isère and onwards to the Rhône. The northernmost section of the massif falls within Switzerland, and

4329-508: The Jardin de Talèfre , its name derives from the rich assemblage of plants which occur at great altitude there (between 2,650 and 3,000 m (8,690 and 9,840 ft)). Described as "one of the loftiest patches of vegetation in Europe upon an islet of rock in the midst of a wilderness of snow and ice", it is higher than the adjacent ground by tens of metres and, as a result, was spared glacial scouring and subsequent loss of its vegetation during

4446-1030: The Little Ice Age (between 1300 and 1850). Nevertheless, it would at that time still have been surrounded by ice on all three sides, as evidenced by the three glacial moraines found there today. Species recorded there include: Achillea nana ; Alchemilla pentaphylla ; Arenaria biflora  [ de ] ; Arenaria serpyllifolia ; Cardamine alpina ; Draba frigida ; Empetrum nigrum ; Epilobium alpinum ; Helictotrichon versicolor  [ pl ] ; Homogyne alpina ; Jacobaea incana ; Juncus trifidus ; Kalmia procumbens ; Poa laxa  [ pl ] ; Potentilla frigida  [ de ] ; Ranunculus glacialis ; Ranunculus pyrenaeus  [ de ] ; Saxifraga aspera ; Saxifraga bryoides ; Saxifraga oppositifolia ; Sedum alpestre  [ es ] ; Sibbaldia procumbens and Trifolium alpinum . The Saussurea Alpine Botanical Garden above Courmayeur

4563-556: The Pennine Alps and the Bernese Alps . The first ascent of Mont Blanc in 1786 by Jacques Balmat and Michel Paccard initiated the sport of alpine mountaineering, and it was during the golden age of alpinism (1854–65) and the silver age of alpinism (1865–82) that the majority of the main summits of the massif were first attained. Members of the England-based Alpine Club were instrumental in many of

4680-455: The Solvay conference of that year, measurements of the energy spectra of beta particles (electrons) were reported, showing that there is a strict limit on the energy of electrons from each type of beta decay. Such a limit is not expected if the conservation of energy is invalid, in which case any amount of energy would be statistically available in at least a few decays. The natural explanation of

4797-520: The Standard Model (see table at right). The current best measurement of the number of neutrino types comes from observing the decay of the Z boson . This particle can decay into any light neutrino and its antineutrino, and the more available types of light neutrinos, the shorter the lifetime of the Z ;boson. Measurements of the Z lifetime have shown that three light neutrino flavors couple to

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4914-523: The cosmic neutrino background (CNB). R. Davis and M. Koshiba were jointly awarded the 2002 Nobel Prize in Physics. Both conducted pioneering work on solar neutrino detection, and Koshiba's work also resulted in the first real-time observation of neutrinos from the SN 1987A supernova in the nearby Large Magellanic Cloud . These efforts marked the beginning of neutrino astronomy . SN 1987A represents

5031-529: The muon neutrino (already hypothesised with the name neutretto ), which earned them the 1988 Nobel Prize in Physics . When the third type of lepton, the tau , was discovered in 1975 at the Stanford Linear Accelerator Center , it was also expected to have an associated neutrino (the tau neutrino). The first evidence for this third neutrino type came from the observation of missing energy and momentum in tau decays analogous to

5148-405: The proton and the electron . He considered that the new particle was emitted from the nucleus together with the electron or beta particle in the process of beta decay and had a mass similar to the electron. James Chadwick discovered a much more massive neutral nuclear particle in 1932 and named it a neutron also, leaving two kinds of particles with the same name. The word "neutrino" entered

5265-454: The 2015 Nobel Prize for Physics for their landmark finding, theoretical and experimental, that neutrinos can change flavors. As well as specific sources, a general background level of neutrinos is expected to pervade the universe, theorized to occur due to two main sources. Around 1 second after the Big Bang , neutrinos decoupled, giving rise to a background level of neutrinos known as

5382-593: The 5th century AD, they had left completely. The areas left behind were occupied in the western part by the Burgundian tribes from what is today France, whilst the Alemanni tribes from Germany moved into eastern parts, resulting in the linguistic divide found today across the Alps. For many centuries thereafter, the settlements around the Mont Blanc massif comprised a rural population of peasant mountain farmers, living off animal husbandry , supplemented with

5499-433: The Chamonix valley by Charles Albert of Sardinia for reconstructing the towns of Sallanches and Cluses , both of which had at that time just been destroyed by fires. The massif has been an important source of mineral specimens for crystal -hunters for over 250 years. The mountaineer and explorer, Edward Whymper , noted that the basin of the Glacier de Talèfre was "considered good hunting-ground for crystals", and that

5616-549: The Miage Glacier and the Brenva Glacier, are very heavily covered in rock debris. The massif is itself defined by broad valleys which formed along fault lines and which have subsequently been shaped by ice during the last glacial period of the ice age. During the mid-19th century the granite of the Mont Blanc massif was an important source of stone for buildings; one hundred Italian stonemasons were brought to

5733-657: The Miage Glacier is Italy's longest glacier and also the largest debris-covered glacier in Europe. Other large glaciers include the Argentière Glacier (9 km (5.6 mi)), the Saleina Glacier (6 km (3.7 mi)), Trient Glacier (4 km (2.5 mi)), the Bossons Glacier ( c. 4 km (2.5 mi)) and the Brenva Glacier. Whilst these glaciers appear to show similar fluctuations in length, research shows that each glacier of

5850-469: The Mont Blanc massif are: The Mont Blanc massif includes eleven independent and six subsidiary summits over 4,000 metres (13,123 ft) in height. These (including Mont Blanc) are shared between Italy and France only, the highest in Switzerland being the Aiguille d'Argentière. The massif is amongst the three major subranges of the Alps having the highest concentration of four-thousanders, together with

5967-599: The Mont Blanc massif has its own individual and distinctive response time to changes in snowfall and climate. The Bossons Glacier is known to respond first, then the Argentière and the Trient Glaciers respond four to seven years later, with the Mer de Glace reacting last —between eleven and fifteen years after changes are first observed in the movement of ice in the Bossons Glacier. Even the smallest glaciers can have

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6084-496: The Mont Blanc massif, all of which can be easily reached or viewed. Glaciers cover 170 square kilometres (66 sq mi) of the massif, of which 110 km (42 sq mi) fall within France. The Mer de Glace is the largest glacier in the western Alps , and the second largest in Europe. It has a total length of 12 km (7.5 mi) from highest snowfield to terminus and an area of 35–40 km (14–15 sq mi). At around 10 km (6 mi) in length,

6201-471: The Mont Blanc massif: Seven of the massif's largest indigenous mammal species are housed in the Merlet Animal Park near Les Houches, including ibex, chamois, marmot, fallow and roe deer . Located 600 metres (2,000 ft) above the village, the park was founded in 1968 and contains eighty animal species from mountain habitats around the world. The region in which the Mont Blanc massif

6318-533: The Rocher Rouges, high up on Mont Blanc, during an expedition organised by Joseph Hamel  [ de ] . Forty years later the remains of two of them were discovered, re-exposed within fissures in the Bossons glacier. They were 3,000 metres (9,800 ft) lower down from the point where they were lost; the corpse of the third guide was discovered the following year. In 2014, a group of climbers found

6435-642: The Tour of Mont Blanc. When Savoy was eventually annexed to France in 1860, Napoleon III and Empress Eugénie visited the region to mark the event and undertook to enhance road access leading to the end of the Arve valley. The 19th century saw considerable economic development which turned the small agricultural town of Chamonix into a base for tourists, with luxurious hotels and mountain lodges being built to accommodate them. A trade in selling local items to visiting foreigners soon developed. Crystals collected from across

6552-537: The Z. The correspondence between the six quarks in the Standard Model and the six leptons, among them the three neutrinos, suggests to physicists' intuition that there should be exactly three types of neutrino. There are several active research areas involving the neutrino with aspirations of finding: International scientific collaborations install large neutrino detectors near nuclear reactors or in neutrino beams from particle accelerators to better constrain

6669-436: The accumulated steeps; Amongst many other notable visitors were: Goethe (1779); Chateaubriand (1805); Madame de Staël ; Victor Hugo ; Louis Pasteur and Franz Liszt (1836), plus two successive wives of Napoleon Bonaparte : Joséphine de Beauharnais (1810) and Marie Louise of Austria (1814). In 1849, John Ruskin spent a month in Chamonix, from where he painted some of the massif's mountains before undertaking

6786-529: The beta decay leading to the discovery of the electron neutrino. The first detection of tau neutrino interactions was announced in 2000 by the DONUT collaboration at Fermilab ; its existence had already been inferred by both theoretical consistency and experimental data from the Large Electron–Positron Collider . In the 1960s, the now-famous Homestake experiment made the first measurement of

6903-471: The beta decay spectrum as first measured in 1934 was that only a limited (and conserved) amount of energy was available, and a new particle was sometimes taking a varying fraction of this limited energy, leaving the rest for the beta particle. Pauli made use of the occasion to publicly emphasize that the still-undetected "neutrino" must be an actual particle. The first evidence of the reality of neutrinos came in 1938 via simultaneous cloud-chamber measurements of

7020-589: The border turns southwards over the Dômes de Miage and Aiguille de Tré la Tête before dropping down to the Col de la Seigne. North of Mont Dolent the border between France and Switzerland meanders roughly north-northwestwards along a ridge-line of slightly lower peaks, including the Aiguille d'Argentière , the Aiguille du Chardonnet and the Aiguille du Tour , before dropping down to the Col de Balme. The Swiss – Italian border runs southwest from Mont Dolent, down to

7137-409: The concept. For the case of neutrinos this theory has gained popularity as it can be used, in combination with the seesaw mechanism , to explain why neutrino masses are so small compared to those of the other elementary particles, such as electrons or quarks. Majorana neutrinos would have the property that the neutrino and antineutrino could be distinguished only by chirality; what experiments observe as

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7254-411: The context of preventing the proliferation of nuclear weapons . Because antineutrinos and neutrinos are neutral particles, it is possible that they are the same particle. Rather than conventional Dirac fermions , neutral particles can be another type of spin  ⁠ 1  / 2 ⁠ particle called Majorana particles , named after the Italian physicist Ettore Majorana who first proposed

7371-448: The earth's crust lifted up schist , gneiss and limestone rocks. These were destined to form the base of the Alps range, and this period of upheaval ended 300   million years ago. Granite intrusions and associated metamorphic rocks formed the base of the mountains we now call the Mont Blanc massif as well as the nearby Aiguilles Rouges . But these rocks were then heavily eroded away, eventually being ground down and inundated by

7488-417: The electron and the recoil of the nucleus. In 1942, Wang Ganchang first proposed the use of beta capture to experimentally detect neutrinos. In the 20 July 1956 issue of Science , Clyde Cowan , Frederick Reines , Francis B. "Kiko" Harrison, Herald W. Kruse, and Austin D. McGuire published confirmation that they had detected the neutrino, a result that was rewarded almost forty years later with

7605-728: The electron neutrino. Neutrinos are fermions with spin of ⁠ 1  / 2 ⁠ . For each neutrino, there also exists a corresponding antiparticle , called an antineutrino , which also has spin of ⁠ 1  / 2 ⁠ and no electric charge. Antineutrinos are distinguished from neutrinos by having opposite-signed lepton number and weak isospin , and right-handed instead of left-handed chirality. To conserve total lepton number (in nuclear beta decay), electron neutrinos only appear together with positrons (anti-electrons) or electron-antineutrinos, whereas electron antineutrinos only appear with electrons or electron neutrinos. Neutrinos are created by various radioactive decays ;

7722-405: The electron neutrinos produced in the Sun had partly changed into other flavors which the experiments could not detect. Although individual experiments, such as the set of solar neutrino experiments, are consistent with non-oscillatory mechanisms of neutrino flavor conversion, taken altogether, neutrino experiments imply the existence of neutrino oscillations. Especially relevant in this context are

7839-451: The electron. More formally, neutrino flavor eigenstates (creation and annihilation combinations) are not the same as the neutrino mass eigenstates (simply labeled "1", "2", and "3"). As of 2024, it is not known which of these three is the heaviest. The neutrino mass hierarchy consists of two possible configurations. In analogy with the mass hierarchy of the charged leptons, the configuration with mass 2 being lighter than mass 3

7956-600: The existence of all three neutrino flavors and found no deficit. A practical method for investigating neutrino oscillations was first suggested by Bruno Pontecorvo in 1957 using an analogy with kaon oscillations; over the subsequent 10 years, he developed the mathematical formalism and the modern formulation of vacuum oscillations. In 1985 Stanislav Mikheyev and Alexei Smirnov (expanding on 1978 work by Lincoln Wolfenstein ) noted that flavor oscillations can be modified when neutrinos propagate through matter. This so-called Mikheyev–Smirnov–Wolfenstein effect (MSW effect)

8073-692: The first ascents, usually accompanied by guides from Chamonix or Courmayeur, such as Michel Croz , Michel Payot and Émile Rey , as well as the Swiss guide, Christian Almer . Across the massif there are now more than two thousand different mountaineering routes to the summits, ranging greatly in both length and difficulty. These attract climbers from all over the world who, unlike the early ascensionists, now have access to numerous climbing guidebooks, modern safety equipment, good information on climbing routes and technical difficulty, as well as weather forecasts and mountain accommodation and food. A wide range of glaciers and glacial structures can be found across

8190-486: The flux of electron neutrinos arriving from the core of the Sun and found a value that was between one third and one half the number predicted by the Standard Solar Model . This discrepancy, which became known as the solar neutrino problem , remained unresolved for some thirty years, while possible problems with both the experiment and the solar model were investigated, but none could be found. Eventually, it

8307-451: The following list is not exhaustive, but includes some of those processes: The majority of neutrinos which are detected about the Earth are from nuclear reactions inside the Sun. At the surface of the Earth, the flux is about 65 billion ( 6.5 × 10 ) solar neutrinos , per second per square centimeter. Neutrinos can be used for tomography of the interior of the Earth. The neutrino

8424-409: The following species of flowering plants amongst rocky debris around permanent snow fields and the highest alpine glaciers: Achillea nana  [ fr ] ; Achillea atrata ; Gentiana nivalis ; Juncus trifidus ; Ranunculus glacialis ; Saxifraga biflora  [ de ] and Saxifraga oppositifolia . In the mid-1800s, Venance Payot , a Chamonix naturalist , published

8541-423: The glacier is now a cause of serious concern. The inexorable downward movement and melting of glaciers can result in objects lost within them reappearing many years later. The first recorded account of a body reappearing from a glacier in the Mont Blanc range was made by Viscount Edmond de Catelin in 1861. It concerned three alpine guides who were buried in a crevasse during an avalanche on 20 August 1820 near

8658-432: The highest point at 4,808 metres (15,774 ft). Whilst the Mont Blanc massif does not contain any species that are endemic to it, there are many rare and legally protected species found within its four major habitat zones. These are the: montane forests , sub-alpine, alpine and nival zones . The major habitats are coniferous forests , moors , rock and talus slopes , plus glacial moraines . The biological richness

8775-593: The hydrogen nuclei in the water molecules. A hydrogen nucleus is a single proton, so simultaneous nuclear interactions, which would occur within a heavier nucleus, do not need to be considered for the detection experiment. Within a cubic meter of water placed right outside a nuclear reactor, only relatively few such interactions can be recorded, but the setup is now used for measuring the reactor's plutonium production rate. Very much like neutrons do in nuclear reactors , neutrinos can induce fission reactions within heavy nuclei . So far, this reaction has not been measured in

8892-513: The initial state, then the final state has only matched lepton and anti-lepton pairs: electron neutrinos appear in the final state together with only positrons (anti-electrons) or electron antineutrinos, and electron antineutrinos with electrons or electron neutrinos. Antineutrinos are produced in nuclear beta decay together with a beta particle (in beta decay a neutron decays into a proton, electron, and antineutrino). All antineutrinos observed thus far had right-handed helicity (i.e., only one of

9009-911: The landscape ground down and shaped the mountains and the valleys as seen today. Both the Mont Blanc massif, and the Aiguilles Rouges range to its north, now form part of the external zone of the Alps, effectively being the outermost layers of rock. The central granites make up Mont Blanc, the steep slopes of the Drus , the Grandes Jorasses and the Dent du Géant, and at the highest points are topped by schists, which are visible in places such as Grands Montets and near Mont Blanc's summit. The granite mountains around Chamonix have been eroded into steep needle-shaped peaks (known as aiguilles ). Known locally as protogine , these rocks are lower in

9126-505: The main building commemorates the discovery. The experiments also implemented a primitive neutrino astronomy and looked at issues of neutrino physics and weak interactions. The antineutrino discovered by Clyde Cowan and Frederick Reines was the antiparticle of the electron neutrino. In 1962, Leon M. Lederman , Melvin Schwartz , and Jack Steinberger showed that more than one type of neutrino exists by first detecting interactions of

9243-456: The massif were much in demand, as were locally produced goods such as horn trinkets and honey. Neutrino A neutrino ( / nj uː ˈ t r iː n oʊ / new- TREE -noh ; denoted by the Greek letter ν ) is an elementary particle that interacts via the weak interaction and gravity . The neutrino is so named because it is electrically neutral and because its rest mass

9360-483: The massif were used as communication routes by the Romans until they left around the 5th century AD. The region remained of some military importance through to the mid-20th century. A peasant farming economy operated within these valleys for many centuries until the glaciers and mountains were "discovered" by the outside world in the 18th century. Word of these impressive sights began to spread, and Mont Blanc

9477-418: The massif's great overall height, a considerable proportion is permanently glaciated or snow-covered and is exposed to extremely cold conditions. Even on the high passes of the Tour du Mont Blanc, around 2,000 to 2,500 m (6,600 to 8,200 ft), summer temperatures can be between 5 and 15 °C (41 and 59 °F), but feeling much colder because of wind chill in windy or wet conditions. Precipitation

9594-403: The massif, from the valley bottoms right up to 3,800 m (12,500 ft) where the alpine chrysanthemum ( Leucanthemopsis alpina  [ fr ] ) can be found at a record-breaking height. Early explorers, such as Alexander von Humboldt in 1807, observed a number of notable species in the mountains around Mont Blanc at altitudes above 3,100 metres (10,200 feet). This was well above

9711-621: The mid-way station of the Skyway Monte Bianco , or on foot from La Palud within two hours and an ascent of 800 m (2,600 ft). The botanical garden derives its name from the genus of mountain flowers, Saussurea (Saw-worts) which itself was named after Horace-Bénédict de Saussure , whose enthusiasm for scientific research in the mountains led to the first ascent of Mont Blanc in 1786. The mountains around Mont Blanc are home to many mammal species, including ibex, chamois , deer, mountain hare and alpine marmot (including

9828-453: The mineral biotite mica and richer in quartz than the granites commonly found elsewhere. A large part of the massif is covered by ice fields and is cut by numerous glaciers, mostly flowing northwestwards on the French side; southeastwards on the Italian side and eastwards on the Swiss side. With much steeper slopes on the Italian side, many glaciers drop very sharply and some, such as

9945-425: The modern Tour du Mont Blanc walking trail still follow the route of a Roman road along the Col du Bonhomme and the Col de la Seigne. The Romans occupied Martigny to the north of the massif, and their influence spread out well beyond the Alps into much of northern Europe. As a result of aggressive pressure from tribes in the north, the imperial forces of Rome were gradually withdrawn from the alpine regions until, by

10062-462: The months of November and April. The best weather for mountaineering or hiking occurs between late June to early October but, being the highest part of the Alps, the Mont Blanc massif can create its own weather patterns. Temperatures drop as the mountains gain in height, and the summit of Mont Blanc is a permanent ice cap, with temperatures around −20 °C (−4 °F). The summit is also prone to strong winds and sudden weather changes. Because of

10179-399: The mountains is facilitated by cable cars , mountain railways and mountain huts which offer overnight refuge to climbers and skiers. The long-distance Tour du Mont Blanc hiking trail circumnavigates the whole massif in an 11-day trek of 170 kilometres (110 mi). The Mont Blanc Tunnel connects the French town of Chamonix on the northern side with the Italian town of Courmayeur in

10296-416: The mountains of the Mont Blanc range to the attention of a wide audience for the first time. In 1760, Horace-Bénédict de Saussure offered a large financial prize to the first people who successfully ascended Mont Blanc. The summit was finally attained on 8 August 1786 by two Chamonix men, the guide Jacques Balmat and Dr. Michel Paccard . The decades that followed saw the gradual opening up of Chamonix to

10413-730: The name Alpes Penninae , or Poeninae , to the highest parts of the Alps—which extended from Mont Blanc to Monte Rosa . They took over Aosta from the Salassi Celtic tribe in 25 AD and engineered roads which extended northwards into Europe via the Great St Bernard Pass and the Little St Bernard Pass . Courmayeur, on the southern side of the massif, began to develop as a stop-off along their trans-alpine trading routes between Italy and France. Parts of

10530-513: The neutrino masses and the values for the magnitude and rates of oscillations between neutrino flavors. These experiments are thereby searching for the existence of CP violation in the neutrino sector; that is, whether or not the laws of physics treat neutrinos and antineutrinos differently. The KATRIN experiment in Germany began to acquire data in June 2018 to determine the value of the mass of

10647-404: The neutrinos by having opposite signs of lepton number and opposite chirality (and consequently opposite-sign weak isospin). As of 2016, no evidence has been found for any other difference. So far, despite extensive and continuing searches for exceptions, in all observed leptonic processes there has never been any change in total lepton number; for example, if the total lepton number is zero in

10764-609: The northern side of the Swiss Alps . The climate of the Mont Blanc massif is cold and temperate ( Köppen climate classification Cfb ), and is greatly influenced by altitude. The main valley settlements around the perimeter of the massif are at an altitude ranging between 600 and 1,200 metres (2,000 and 3,900 ft). Daytime valley temperatures in July and August may range up to 25 °C (77 °F), sometimes reaching 30 °C (86 °F). The greatest snowfall occurs between

10881-578: The only verified detection of neutrinos from a supernova. However, many stars have gone supernova in the universe, leaving a theorized diffuse supernova neutrino background . Neutrinos have half-integer spin ( ⁠ 1  / 2 ⁠ ħ ); therefore they are fermions . Neutrinos are leptons. They have only been observed to interact through the weak force , although it is assumed that they also interact gravitationally. Since they have non-zero mass, theoretical considerations permit neutrinos to interact magnetically, but do not require them to. As yet there

10998-497: The permanent snow line, but on rocks that were so steep that little snow could rest. These arctic-alpine species included: Androsace carnea  [ es ] ; Androsace chamaejasme  [ de ] ; Arabis caerulea  [ de ] ; Cardamine bellidifolia ; Draba hirta ; Saxifraga androsacea  [ es ] and Silene acaulis (occurring down to 1,500 m (4,900 ft)). Between 2,500 and 3,100 m (8,200 and 10,200 ft), Humboldt noted

11115-409: The probability for an interaction. In general the interaction probability increases with the number of neutrons and protons within a nucleus. It is very hard to uniquely identify neutrino interactions among the natural background of radioactivity. For this reason, in early experiments a special reaction channel was chosen to facilitate the identification: the interaction of an antineutrino with one of

11232-488: The public in 2006 and tells the story of the early crystal-hunters (known as cristalliers ). Many specimens collected from across the massif are displayed there. Located on the watershed between the Rhône and the Po , the Mont Blanc massif is also situated between the two different climatic regions of the northern and western Alps and that of the southern Alps. Climatic conditions on the Mer de Glace are similar to those found on

11349-688: The pure flavor states produced has been found to depend profoundly on the flavor. The relationship between flavor and mass eigenstates is encoded in the PMNS matrix . Experiments have established moderate- to low-precision values for the elements of this matrix, with the single complex phase in the matrix being only poorly known, as of 2016. A non-zero mass allows neutrinos to possibly have a tiny magnetic moment ; if so, neutrinos would interact electromagnetically, although no such interaction has ever been observed. Neutrinos oscillate between different flavors in flight. For example, an electron neutrino produced in

11466-428: The reactor experiment KamLAND and the accelerator experiments such as MINOS . The KamLAND experiment has indeed identified oscillations as the neutrino flavor conversion mechanism involved in the solar electron neutrinos. Similarly MINOS confirms the oscillation of atmospheric neutrinos and gives a better determination of the mass squared splitting. Takaaki Kajita of Japan, and Arthur B. McDonald of Canada, received

11583-947: The scientific vocabulary through Enrico Fermi , who used it during a conference in Paris in July ;1932 and at the Solvay Conference in October ;1933, where Pauli also employed it. The name (the Italian equivalent of "little neutral one") was jokingly coined by Edoardo Amaldi during a conversation with Fermi at the Institute of Physics of via Panisperna in Rome, in order to distinguish this light neutral particle from Chadwick's heavy neutron. In Fermi's theory of beta decay , Chadwick's large neutral particle could decay to

11700-564: The sea, so allowing sedimentary rocks to form. Then, once again, this part of the Earth's crust was uplifted as a result of the collision of continental plates . The huge mountain ranges of today's Alps began to form. This happened towards the end of the Tertiary period, 15   million years ago. Finally, came the Quaternary era, when successive ice ages saw vast glaciers advance, retreat, and then advance again. Their movement across

11817-436: The site of one of two Air India plane crashes. These occurred at almost identical locations high up near the summit of Mont Blanc: one in 1950 ( Air India Flight 245 ), and one in 1966 ( Air India Flight 101 ). Debris from these crashes is still commonly found on the glacier below. The Mont Blanc massif consists predominantly of ancient granite rocks. The Alps have their origins 770   million years ago when upheaval of

11934-512: The slopes below les Courtes had yielded many large specimens. He recounted that in 1745 a guide had stated he had collected over 300 pounds (136 kg) of specimens there in just three hours. The first systematic account of the minerals of the Mont Blanc area was published in 1873 by Venance Payot. His list, entitled "Statistique minéralogique des environs du Mt-Blanc", catalogued 90 mineral types although it also included those present only as very small components of rocks. If these are excluded, it

12051-432: The south. The high mountains have provided many opportunities for scientific research, including neutrino measurements within the tunnel and impact of climate change on its highest slopes. Recent rises in average temperatures have led to significant glacial retreat across the massif and an awareness of the need for better environmental protection, including a call for World Heritage Site status. The Mont Blanc massif

12168-496: The summit of Mont Dolent at an altitude of 3,820 metres (12,533 ft). From here the French – Italian border runs southwestwards along a ridge of high summits on the southern side of the massif, many of which are over 4,000 metres (13,123 ft) in height, including the Grandes Jorasses , Rochefort Ridge , Dent du Géant , Mont Maudit , Mont Blanc and its western satellite, the Aiguille de Bionnassay . From here

12285-589: The summit of Mont Blanc) precipitation is considerably less, with only around 1,100 mm (43 in) recorded, despite the latter measurements being taken at a height of 4,300 metres (14,100 ft). In the mountains further south of the Mont Blanc range, annual precipitation is significantly less than at equivalent altitudes within the massif. For example, the valleys in the Pelvoux massif at around 1,000 metres (3,300 ft) receive only around 600 to 700 mm (24 to 28 in) of precipitation per year, which

12402-455: The true extent of the upper valley. The broadest definition makes the start upstream of Sallanches, including Passy and the valleys of Mégève, Montjoie, and Chamonix. This also describes the region of "Mont Blanc country" (Pays du Mont Blanc.) Some consider the upper valley to only include the valley of Chamonix. This valley stretches, from downstream, through the communes of Servoz, Les Houches, Chamonix-Mont-Blanc and Vallorcine. Historically,

12519-421: The twin passes of Col Ferret. The massif contains 11 main summits over 4,000 metres (13,123 ft) in altitude, as well as numerous subsidiary points above this height. Crowning the massif is Mont Blanc (4,808 metres (15,774 ft)), the highest mountain in the Alps and in western Europe. From the summit of Mont Blanc to the Arve near Chamonix there is a 3,800 metres (12,500 ft) drop in altitude over

12636-449: The two possible spin states has ever been seen), while neutrinos were all left-handed. Antineutrinos were first detected as a result of their interaction with protons in a large tank of water. This was installed next to a nuclear reactor as a controllable source of the antineutrinos (see Cowan–Reines neutrino experiment ). Researchers around the world have begun to investigate the possibility of using antineutrinos for reactor monitoring in

12753-722: The valley was a part of Farcigny, which was ceded to the Count of Savoie during the reign of Amadeus VI in 1355. The bottom of the valley is heavily urbanised including the cities/towns of: Mont Blanc massif The Mont Blanc massif ( French : Massif du Mont-Blanc ; Italian : Massiccio del Monte Bianco ) is a mountain range in the Alps , located mostly in France and Italy , but also straddling Switzerland at its northeastern end. It contains eleven major independent summits, each over 4,000 metres (13,123 ft) in height. It

12870-400: The vast catchments of the rivers Rhône and Po , and a tripoint between France, Italy and Switzerland; it also marks the border between two climate regions by separating the northern and western Alps from the southern Alps. The mountains of the massif consist mostly of granite and gneiss rocks and at high altitudes the vegetation is an arctic-alpine flora. The valleys that delimit

12987-599: The west it is bounded by the Val Montjoie, containing Les Contamines-Montjoie and the river Le Bon Nant which flows northwards to a confluence with the Arve near Saint-Gervais-les-Bains , and onwards to the Rhône . The southern side of the massif lies mostly within Italy and is bounded by the Val Veny and Val Ferret whose watercourses meet just above Courmayeur . From Courmayeur these waters flow southwards as

13104-464: The world, as well as the rest of the Mont Blanc massif. The many published accounts of climbs and impressive sights amongst or around the mountain range attracted numerous wealthy and notable visitors, for whom a visit to marvel at the Sea of Ice (the Mer de Glace) became a fashionable thing to experience. In July 1816, Mary Shelley and Percy Bysshe Shelley toured the Alps and visited Chamouni (as it

13221-492: Was first climbed in 1786, marking the start of the sport of mountaineering. The region is now a major tourist destination, drawing in over six   million visitors per year. It provides a wide range of opportunities for outdoor recreation and activities such as sight-seeing, hiking , rock climbing , mountaineering and skiing . Around one hundred people a year die across its mountains and, occasionally, bodies have been lost and entombed in its glaciers for decades. Access into

13338-428: Was inspired by the river Arve, the snow-covered summits, the chaotic glaciers and the forests that he experienced during their visit. Far, far above, piercing the infinite sky, Mont Blanc appears—still, snowy, and serene— Its subject mountains their unearthly forms Pile around it, ice and rock; broad vales between Of frozen floods, unfathomable deeps, Blue as the overhanging heaven, that spread And wind among

13455-423: Was postulated first by Wolfgang Pauli in 1930 to explain how beta decay could conserve energy , momentum , and angular momentum ( spin ). In contrast to Niels Bohr , who proposed a statistical version of the conservation laws to explain the observed continuous energy spectra in beta decay , Pauli hypothesized an undetected particle that he called a "neutron", using the same -on ending employed for naming both

13572-404: Was realized that both were actually correct and that the discrepancy between them was due to neutrinos being more complex than was previously assumed. It was postulated that the three neutrinos had nonzero and slightly different masses, and could therefore oscillate into undetectable flavors on their flight to the Earth. This hypothesis was investigated by a new series of experiments, thereby opening

13689-544: Was then known), as well as the Mer de Glace and the Bossons Glacier. They jointly published their accounts and letters in a work entitled: History of a Six Weeks' Tour through a part of France, Switzerland, Germany, and Holland; with Letters Descriptive of a Sail Round the Lake of Geneva and of the Glaciers of Chamouni . The book concludes with Mont Blanc , a 144-line poem by Percy Shelley, written whilst in Chamonix and which

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